
* {
    margin: 0;
    padding: 0;
    box-sizing:border-box;
}
li {
    list-style: none;
}
.product {
    width: 800px;
    margin: 0 auto;
    height: 100px;
    background-color: green;
}

#nav {
    width: 100%;
    height: 100px;
    background-color: #ccc;
    overflow: hidden;    
}

ul {
    width: 1280px;
    height: 100%;
}
li {
    position: relative;
    float: left;
    width: 240px;
    height: 60px;
    margin: 20px 0;
    text-align: center;
    line-height: 60px;
    &+li {
        margin-left: 20px;
    }
    &:nth-child(1) {
        background-color: yellowgreen;
    }
    &:nth-child(2) {
        background-color: greenyellow;
    }
    &:nth-child(3) {
        background-color: gold;
    }
    &:nth-child(4) {
        background-color: plum;
    }
    &:nth-child(5) {
        background-color: skyblue;
    }
}
.line {
    position: absolute;
    top: 0;
    left: 50%;
    width: 1px;
    height: 100%;
    background-color: blue;
}

.center {
    width: 1px;
    height: 100px;
    margin: 0 auto;
    background-color: red;
}